Operating mechanism for a circuit interrupter with toggle means continuously in underset condition

ABSTRACT

An operating mechanism for a circuit breaker is provided having a rotatable main lever, which is rotated to a closed position by an actuator, such as a piston, movable within a cylinder, and is maintained in the closed position by a latching device, such as a collapsible linkage maintained in its extended position by a magnetic trip device. The arrangement functions, during an opening operation, to actuate the tripping device, which permits collapse of the linkage and opening rotative motion of the main lever. During a subsequent closing, the piston device provides the energy for rotating the main lever to its closed position against the opposition provided by accelerating springs, and the collapsible linkage maintains the main lever in the closed position by the magnetic trip.

United States Patent William 11. Fischer Pittsburgh; Wayne S. Aspey,Monroeville, both of Pa. [21] Appl. No. 776,510 [22] Filed Nov. 18,1968[45] Patented Nov. 30, 1971 [73] Assignee Westinghouse ElectricCorporation Pittsburgh, Pa.

[72] Inventors [54] OPERATING MECHANISM FOR A CIRCUIT INTERRUPTER WITHTOGGLE MEANS CONTINUOUSLY IN UNDERSET CONDITION 7 Claims, 14 DrawingFigs.

3,334,202 8/1967 Tognella 200/153 (.8) X

2,562,147 7/1951 Kuwayama 335/174 X 3,023,285 2/1962 Favre .1 335/191 XFOREIGN PATENTS 846,527, 9/1939 France 200/148 (.6)

Primary ExaminerRobert K. Schaefer Assistant Examiner-Robert A.Vanderhye Attorneys-A. T. Stratton, Clement L. McHaIe and Willard R.

Crout ABSTRACT: An operating mechanism for a circuit breaker is providedhaving a rotatable main lever, which is rotated to a closed position byan actuator, such as a piston, movable within a cylinder, and ismaintained in the closed position by a latching device, such as acollapsible linkage maintained in its extended position by a magnetictrip device. The arrangement functions, during an opening operation, toactuate the tripping device, which permits collapse of the linkage andopening rotative motion of the main lever. During a subsequent closing,the piston device provides the energy for rotating the main lever to itsclosed position against the opposition provided by accelerating springs,and the collapsible linkage maintains the main lever in the closedposition by the magnetic trip.

TO HIGH PRESSURE TO LOW PRESSURE COMPRESSOR HIGH PRESSURE LOW PRESSURETO AUXILIARY CONTACTS OPEN PATENTED NUVSO I97! SHEET u 0F 6 FIG. 5.

CLOSED POSITION PATENTEB unvso :97:

SHEET 5 0F 6 OPEN POSITION FIG.6.

OPERATING MECHANISM FOR A CIRCUIT INTERRUPTER WITII TOGGLE MEANSCONTINUOUSLY IN UNDERSET CONDITION CROSS-REFERENCES TO RELATEDAPPLICATIONS BACKGROUND OF THE INVENTION As well known by those skilledin the art, in a circuit breaker mechanism it is desirable to providefor a straight closing operation, a straight opening operation, and forvarious duty cycles, such as open-close, close-open, and openclose-open.These functions must be provided quickly for opening the circuit in theorder of two cycles. This is necessary to prevent continuous flow offault current through the line, and to prevent a loss of synchronism ofassociated equipment.

Not only must the operating mechanism for a circuit breaker perform theaforesaid duty cycles, but, in addition, it must be reliable, preferablysimple, require little maintenance, and be completely safe to protectoperating personnel.

SUMMARY OF THE INVENTION According to a preferred embodiment of theinvention, there is provided a rotatable main lever, which isstationarily mounted between the side plates of a main frame. The mainlever has an arm portion which is connected to the several phases of thecircuit-breaker structure to cause the actuation of either the contactstructure thereof, or of control valves associated, with the respectivephases. In addition, the main rotatable operating lever has alatching-arm portion, which is maintained in the closed position by acollapsible toggle linkage which, in turn, is.maintained in a slightlyunderset condition by a trigger actuated by a magnetic tripping device.To effect the closing rotative motion of the main operating lever, thereis provided anactuator, such as a piston, movable by gas pressure withinan operating cylinder to cause abutment with another arm-portionof themain operating lever to cause the closing rotation thereof.

Accelerating springs associated with either the contact structure, orwith the control valves bias the operating lever to the open position,but it is maintained in its closed biased position until release of thetripping magnet by energization of tripping coils.

Accordingly, it is a general purpose of the present invention to providean improved operating mechanism for a circuit interrupter, preferablyone of the high-voltage type.

Another object of the present invention is the provision of an improvedhigh-speed operating mechanism for a circuit interrupter, which isreliable in operation and composed of relatively few parts.

Still a further object of the present invention is the provision of animproved operating mechanism for a circuit interrupter, which requireslittlemaintenance and provides fast opening and closing operations.

Further objects and advantages will readily become apparent uponreadingthe following specification taken in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an end elevational view of a3-phase circuit interrupter, of the high-voltage type, utilizing theimproved operating mechanism of the present invention;

FIG. 2 is a side elevational view of the 3-phase circuit interrupterofFIG. 1;

FIG. 3 is a top plan-view of the 3-phase circuit interrupter of FIGS. 1and 2; K

FIG. 4 is a diagrammatic view illustrating the interconnectingmechanical linkage between the operating mechanism, or

ground potential operator. and the control valves associated with eachof the phase-units of the circuit interrupter;

FIG. 5 is an enlarged side elevational view of the improved operatingmechanism of the present invention, the parts being indicated in theclosed position;

FIG. 6 is a view similar to that of FIG. 5, but illustrating thedisposition of the several parts in the fully open-circuit position;

FIG. 7 is a detailed view of the tripping lever for the mechanism;

FIG. 8 is a plan view of the tripping lever of FIG. 7;

FIG. 9 is a side elevational view of the tripping magnet of theoperating mechanism;

FIG. 10 is atop plan view of the tripping magnet for FIG. 9;

FIG. II is a side elevational view of the magnet structure of theelectromagnetic tripping mechanism, with the armature being shown in thereleased position;

FIG. 12 is a diagrammatic view illustrating the cooperation between theoperating mechanism of the present invention through the interconnectinglinkage to the 3-way control valves associated with each of the phaseunits, and a diagrammatic representation of the manner of contactoperation;

FIG. 13 is a diagrammatic view showing the utilization of 5 theoperating mechanism of the present invention in conjunction with asimple actuation of contact structure for a 3phase circuit interrupter;and,

FIG. 14 is a wiring diagram suitable for use with the improved operatingmechanism of the present invention, and adapting the same to reclosingoperations.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, andmore particularly to FIGS. 1-3 thereof, it will be observed that thereis illustrated a 3- phase circuit interrupter of the high-voltage type,generally designated by the reference numeral 1. With particularreference being directed to FIGS. 2 and 3 of the drawings, it will benoted that there is provided three circuit-interrupting phase-unitsdesignated by the reference letters A, B and C. The three phase-unitsare mounted upon a stationary sturdy frame support composed of heavystructural channel members, generally designated by the referencenumeral 3, and comprising upstanding supporting members 4 and andlateral braces 5.

It will be noted that each phase-unit generally, comprises a groundedhousing structure 7 and slantingly upwardly extending arc-extinguishingassemblages 9 and terminal-bushing structures 10. As a result, theelectrical circuit extends in a general U" manner from the line terminal11 downwardly through the arc-extinguishing assemblage 9, and through apressurized conduit (not shown) disposed within the housing structure 7,and then upwardly toward the right through the terminal-bushingstructure 10. This structure is more detailed in US. Pat. applicationfiled Dec. 9, 1968, Ser. No. 782,365, by Richard Kane and Frank Reese,and assigned to the assignee of the instant application.

Since the present invention is directed to the operating mechanism 13for the circuit-interrupting structure 1, it does not appear necessaryto go into a detailed description of the various parts within thearc-extinguishing assemblage, and, if desired, reference may be had tothe aforesaid US. Pat. application Ser. No. 782,365.

Each of the arc extinguishing assemblages 9 includes one or more pairsof separable contacts, which are pressure actuated by a piston device.This is designated by the reference numeral 15 in FIG. 12 of thedrawings. Tocontrol the opening and closing operations of the pistondevice 15, and hence to effect the opening and closing movement of theseveral contact structures 17 disposed within the arc-extinguishingassemblages 9, 3-way control valves 18 areassociated with each of thearc-extinguishing assemblages 9. The valve rods 19 for controlling eachof the 3-way control valves I8 are mechani cally interconnected,generally horizontally, along the stationary'frame structure 3 in amanner somewhat indicated by FIGS. 4 and 12 of the drawings. Withreference to FIG. 4, it will be seen that each valve-control rod 18 isconnected to a bellcrank operator 20, which is moved by horizontallyinterconnecting rods 21, 22 which are, in turn, actuated by the mainoperating lever 24 of the improved operating mechanism 13 of the presentinvention.

FIG. 12 diagrammatically illustrates the interconnection between themain operating lever 24 of the improved operating mechanism 13 and thehorizontally extending interconnecting links 21, 22. A simplified wiringdiagram is shown in FIG. 12, but for adapting the circuit breaker l toquick opening and reclosing operations, use may be made of a moresophisticated diagram, as illustrated in FIG. 14 of the drawings.

A low-pressure tank 26 is suspended below the main frame support 3 andprovides a reservoir for the low-pressure sulfurhexafluoride (SF gas,which is used in the particular structure. It will, of course, beobvious to those skilled in the art that other gases could be used, suchas compressed air. In addition, the present operating mechanism 13,being described, is not restricted to a compressed-gas circuitinterrupter, but may be used to actuate the contacts directly, asindicated in FIG. 13 of the drawings; and, in fact, the contacts 17associated therewith could be disposed in an oil tank, (not shown) andthe structure, therefore, could be termed an oilcircuit breaker. Inother words, the operating mechanism 13 of the present application hasuniversal application, either to actuate control valves 18 associatedwith a compressed-gas circuit interrupter, or it could be used toactuate the contacts 17 directly in any type of a circuit-interruptingstructure, such as oil, compressed gas, or even an air-break device.

In the structure being described, and as particularly set forth in theaforesaid application Ser. No. 782,365, sulfur-hexafluoride (SF gas isutilized. Since this is an expensive gas, it is desirable to conserveit, and, therefore, a circulating system is provided, in which the usedgas is stored in the low-pressure tank 26, recompressed by a compressorstructure, not shown, and then the high-pressure gas is stored insuitable reservoirs associated with the arc-extinguishing assemblages 9.It is then used for opening the contact.structures and simultaneouslyeffecting an arc-extinguishing flow across the resultant arcsestablished between the pairs of separated contacts. Reference may behad to the aforesaid application Ser. No. 782,365 for a description ofthe manner of circuit interruption utilizing a flow of compressed SFgas. For the purposes of understanding the present invention, however,such a description is deemed unnecessary.

The operating mechanism 13 of the present invention is closelyassociated with the middle phase unit, as designated by the referenceletter B" in FIG. 2 of the drawings. Also FIG. 4 generally shows theassociation of the operating mechanism 13 with the interconnectinglinkage 21, 22 so as to efiect simultaneous operation of all of thecontrol valves 18 associated with the 3-phase-units A, B, and C.

FIGS. and 6 show, in a more detailed manner, the several components ofthe improved operating mechanism 13 of the present invention, FIG. 5showing the disposition of the several parts in the closed position,whereas FIG. 6 shows the parts in the fully open-circuit position. Itwill be noted that, generally, there is provided the rotatable mainoperating lever 24, which is stationarily pivoted on an operating shaft29, which extends between two side plates 30, 31 of a main stationaryframe support 32. -In fact. although the main rotatable lever 24 isindicated as being a single-plate configuration, in fact, it comprisestwo spaced plates welded together for strength, and having a sleevebearing 33 welded thereto, which is used as a bearing structure for thestationary operating shaft 29.

As shown in FIGS. 5 and 6, it will be noted that the main rotatableoperating lever 24 has an actuating-arm portion 24a, which has pivotedthereto an operating link 34 which extends generally laterally, and isconnected to the previously mentioned horizontal linkage structure 21,22.

In addition, the rotatable main operating lever 24 has an actuating-a-rmportion 24b, which supports a roller 35, which is actuated by a pistonrod 36, the piston 37 being disposed interiorly of an operating cylinder38 and operated by high-pressure gas passing through a 3-way controlvalve 40 to the lefthand face of the operating piston 37 to force thesame to the right, and hence to effect a closing rotative motion of themain operating lever 24. This is indicated by the dotted lines in FIGS.5 and 6 of the drawings. A retracting spring 41 is disposed to the rightof the aforesaid piston structure 37 and effects a retraction thereoffollowing a reduction of the gas pressure at the left-hand end of theoperating cylinder 38 following a closing operation.

To maintain the main operating lever 24 in its closed position, asillustrated in FIG. 5 of the drawings, a collapsible toggle linkage 43is provided. As shown in FIG. 5, the collapsible toggle linkage 43comprises a pair of pivotally connected toggle links 45 and 46, theupper toggle link 45 being stationarily mounted upon a stationary pivotpin 48 supported by an upstanding support portion 32a of the mainstationary frame 32. The lower toggle link 46 is pivotally connected at49 to the arm portion 24c of the main operating lever 24. In fact, eachof the toggle links 45, 46 comprises a pair of spaced toggle links forstrength and for facility in mounting the pins and rollers. To latch thecollapsible linkage 43 in a slightly underset position, there isprovided a pivotally mounted trigger lever, generally designated by thereference numeral 50. As shown in more detail in FIGS. 7 and 8, therotatable trigger lever supports an armature 52, which is magneticallymaintained to a tripping magnet 54, as illustrated in FIG. 11 of thedrawings.

Generally, the tripping magnet 54 is such as to beactuated by anenergization of tripping coils 56, 57, which releases the magnetic fluxextending through the armature 52 and thereby permits collapse of thetoggle linkage 43.

A pair of hydraulic shock absorbers, 59, 60 or snubbers are providedhaving actuating-stem portion 590, 60a which engage rollers 61 and 62movable with the main rotatable operating lever 24. This cushions theoperating lever 24 at the extremity of its opening and closing motions.Elements 59, 60 also act as the stops at the full open and closepositions.

As shown in FIGS. 5 and 6, the arm portion 240 has pivotally connectedthereto a link 64, which effects rotation of a rotatably-mounted arm 65,which, in turn, actuates a plurality of auxiliary switches 16 connectedinto the wiring circuit for the mechanism 13.

FIG. 14 illustrates, in detail, a wiring diagram for the operatingmechanism 13 of the present invention, adapting the same for high-speedopening and reclosing operations.

Diagram FIG. 14 is shown in the breaker open position.

To close the circuit breaker the 101 C contact is closed. This completesthe circuit through b, I-IPSX, Y, X time delay relay. Both X contactsclose. This completes the circuit through X, Y, CC (Close Coil), Y, X.The close coil is energized and the breaker closes. At the end of theclose stroke the TI LCH SW contact closes. This completes the circuitthrough Y relay. Two Y contacts close and three Y contacts open. The CC(Close Coil) is deenergized. The X time delay relay is deenergized andboth X contacts open. As long as the C contact is closed the Y relaystays energized and the X relay cannot again be energized. This preventspumping the circuit breaker contacts. The X relay is time delay in caseb should open before TT LCH SW the Y relay will still be energized atthe end of the close stroke.

To open the circuit breaker contact 101 T is closed. This completes thecircuit through HPSX, RPMS, a, a, TC-l, 7.7r resistor. When the ll-poleswitch reaches the breaker open position contacts a, a, open andinterrupt the trip current. If reset piston is not reset the microswitch RPMS will prevent tripping.

The function of HPSX is to prevent tripping or closing should the highpressure SF fall below the minimum pressure allowed for safe operation.

FIG. 12 diagrammatically illustrates the association of the operatingmechanism 13 of the present invention with the3- way control valves 18of the individual arc-extinguishing assemblages 9 associated with thephase-units A, B and C. It will be observed that the three control rods19 are simultaneously actuated, and control the entrance and exhaust ofgas pressure below the actuating pistons 15, which, in turn control themoving contacts 17 of the interrupter. By an upward movement of thecontrol valves 18, high-pressure gas is admitted below the pistons toeffect an opening operation of the contact structure 17.Correspondingly, an exhausting, or dumping of high-pressure gas belowthe pistons 15 will efiect a closing of the contact structure 17, asassisted by the closing springs 68.

Generally, the mechanism 13 is biased to the open position by one ormore accelerating springs 70, such as diagrammatically indicated inFIGS. 12 of the drawings.

From the foregoing description it will be apparent that to effect anopening operation of the interrupter, energization is had of thetripping magnet 54 to effect release of the rotatable trigger arm 50,and a collapse of the toggle linkage 43. This will permit an openingrotative motion of the main operating lever 24, as biased by the severalaccelerating springs 70, with a consequent opening of the 3-way valves18. In the fully open-circuit position, as illustrated in FIG. 6 of thedrawings, the trigger arm 50 remains in its upward position, and is notreset until during the subsequent closing operation. As mentioned,during the opening operation, the valve rods 19 are maintained intheirpiston-exhausting position, as illustrated in FIG. 12, and thecontact structure 17 is maintained in its open position.

To effect a closing operation, the 3-way valve 40 associated with theoperating cylinder 38 is energized to introduce highpressure gas to theleft of the actuating piston 37, which forces the plunger thereof to theright in abutment with the closing roller 35 of the main operating lever24. This effects a counterclockwise closing rotative motion of the mainoperating lever 24, until the toggle linkage 43 is extended, and thelatching portion 50a of the tripping lever 50 again maintains the togglelinkage 43 in its slightly underset condition. A tension spring 71biases the tripping lever 50 in a counter- 'clockwise direction, so thatduring the closing operation, the

armature 52 again confronts the pole plates of the tripping magnet 54.The magnetic force then maintains the armature 52 in its engagedposition, as illustrated in FIG. 5, until the next energization of thetripping coils 56, 57.

TRIP MAGNET ASSEMBLY 54 The trip magnet assembly 54 or magnetic holdinglatch, for releasably magnetically latching the roller 44 of the kneepin 47 in the closed circuit position of the circuit breaker 1 will nowbe described. Generally, the trip magnet assembly 54 comprises a holdingmagnet and a trigger lever 50 pivotally mounted about a stationary pivotshaft 51 and carrying a movable armature 52 at one end thereof, and alatch portion at the other end thereof. As shown more clearly in FIG.11, the holding magnet '54 comprises a generally U-shaped magnetstructure, as shown, and a permanent magnet member 58. The U-shapedmagnetic structure 54 comprises a base part 54a and two pole pieces, orleg parts 54b, 546. A thin layer 63 of nonmagnetic material separatesthe pole pieces 54b, 540 from the base part 54a. Each of the pole pieces54b, 540 is provided with a generally flat pole face against which thearmature 52 seats in the closed position, as shown in FIG. 5. The polepieces 54b, 540, base part 540, and armature 52, are made of a suitablemagnetically permeable material, such as soft iron. The permanent magnet58 is of the ceramic type.

With reference to FIG. 11, which shows the holding magnet 5'4 in thereleased position, it will be noted that theZ-piece pole assemblyprovides two parallel magnetic paths for flux from the ceramic permanentmagnet 58. With the armature 52 in the reset position, most of the fluxconcentrates in the lowreluctance path provided by the moving armature52. The magnet 54 holds this armature with a force of 200 pounds, forexample, opposing a pound force as applied by the roller load 44 throughthe trigger lever 50. Thus, there is provided a [00 percent safetyfactor, for example, to prevent accidental tripping by mechanicalshocks.

To initiate a tripping operation of the pole-unit "A, the trip coilassembly 56, 57 is energized by pressing the manual trip button TBthereby completing the tripping circuit through the battery 112. Or, aswell known by those skilled in the art, the tripping may be initiated bymeans of the trip relay 113 upon the occurrence of an overload currentthrough the line L,L controlled by the breaker l, which overload orfault current causes the relay 113 to close its contacts 114, thuscompleting the tripping circuit through the battery 112.

There are provided two trip coils 56, 57, one around each pole piece54b, 54c, which are connected in series and wound so that themagnetomotive force produced by the coils opposes the permanent-magnetflux in the moving armature 52. This opposition decreases the magneticflux in the moving armature circuit (the permanent-magnet flux transfersfrom the moving armature loop to the parallel upper airgap loop). Theholding force on the armature 52 is reduced, allowing the I00 poundtrigger force to initiate motion for release of the armature triggerlever 50.

Trip coil current is cut off by an auxiliary switch after a smallmovement of the breaker mechanism 13. The armature 52 is reset when themechanism closes.

As stated hereinbefore, when the trip coil 56 is energized, either bymanually pressing the tripping button TB, or by automatic operation ofthe overload current relay 113, the trip-coil magnetomotive forceopposes the magnetomotive force of the permanent magnet 58 in themagnetic path through the armature 52, thereby reducing the flux throughthe armature 52. The magnetic flux of the permanent magnet itselfremains almost constant and transfers" from the armature 52 to the paththrough the air" gaps 63a, 63b and the base part 540, thereby reducingthe force by which the armature 52 is attracted to pole faces 54b and54c and allowing the armature 52, to be opened by the 100 pound forceresulting from the trigger load. The trigger structure 50 will rotate,as a unit, in a clockwise direction about the stationary pivot shaft 51until the force F" exerted by the latching roller 44 collapses thetoggle linkage 43.

From the foregoing description it will be apparent that there has beenprovided an improved high-speed simplified type of operating mechanism13 particularly adapted for high-speed closing and opening operations.In addition, it is adapted for reclosing operations by use of the wiringdiagram of FIG. 14. Moreover, the operating mechanism 13 is suitable notonly for the actuation of control valves 18, but for a direct connectionwith the movable contact structures, as diagrammatically represented inFIG. 13 of the drawings.

The solenoid valve 40a is tilted in such a way that any liquid SP thatforms or drains back into the high-pressure SF source. A latch checkswitch 73 cuts off the current to the solenoid valve. In addition, alatch check switch 74 on the closing cylinder prevents the tripping coilfrom being energized until the piston rod is fully retracted.

The operating mechanism 13 of the present invention is low in cost,meets 2-cycle and duty-cycle ratings, is simple in design, and providesimproved contact synchronization by using only one operator 24 for allthree poles of the device.

It is to be clearly understood that those skilled in the art could makemany changes to the above-described operator without departing from thebasic concept. As an example of this, compressed air could be usedinstead of sulfur hexafluoride gas, or rubber snubbers could be usedinstead of the hydraulic snubbers 59, 60 as indicated. Other changeswould obviously present themselves to one skilled in the art.

Although there has been illustrated and described specific structures,it is to be clearly understood that the same were merely for the purposeof illustration, and that changes and modifications may readily be madetherein by those skilled in the art, without departing from the spiritand scope of the invention.

We claim:

I. An operating mechanism for a circuit interrupter including, incombination:

a. supporting means rotatively supporting a main operating lever on afixed pivot and having rotative opening and closing motions about saidfixed pivot;

b. said operating lever having a latching-arm portion;

c. a collapsible toggle linkage pivotally connected between a stationarypoint and said latching-arm portion and in an underset condition at alltimes;

d. holding means releasably maintaining said collapsible toggle linkagein an underset condition;

e. mea'ns releasing said holding means;

f. an operating rod interconnecting the operating mechanism with thecontact motion and responsive to motion of said operating lever; and,

g. closing means for, at times. effecting the rotative closing motion ofsaid main operating lever about said fixed pivot independently of saidtoggle linkage.

2. The combination of claim 1. wherein the holding means is amagnetically actuated trigger arm.

3. The combination of claim 1, wherein the closing means is apiston'operated device.

4. The combination of claim 1. wherein said operating rod is connectedto a control valve for controlling the operation of piston-actuatedcontacts of the circuit breaker.

5. The combination of claim 1, wherein a pair of shock absorbers cushionthe opening and closing motions of the rotatable main operating lever.

6. The combination according to claim 3, wherein the piston-operateddevice includes a piston reciprocally movable within an operatingcylinder and spring-retracted to its inoperative position.

7. The combination according to claim 2, wherein a fluxshiftermagnetically releases an armature attached to the trigger arm.

1. An operating mechanism for a circuit interrupter including, incombination: a. supporting means rotatively supporting a main operatinglever on a fixed pivot and having rotative opening and closing motionsabout said fixed pivot; b. said operating lever having a latching-armportion; c. a collapsible toggle linkage pivotally connected between astationary point and said latching-arm portion and in an undersetcondition at all times; d. holding means releasably maintaining saidcollapsible toggle linkage in an underset condition; e. means releasingsaid holding means; f. an operating rod interconnecting the operatingmechanism with the contact motion and responsive to motion of saidoperating lever; and, g. closing means for, at times, effecting therotative closing motion of said main operating lever about said fixedpivot independently of said toggle linkage.
 2. The combination of claim1, wherein the holding means is a magnetically-actuated trigger arm. 3.The combination of claim 1, wherein the closing means is apiston-operated device.
 4. The combination of claim 1, wherein saidoperating rod is connected to a control valve for controlling theoperation of piston-actuated contacts of the circuit breaker.
 5. Thecombination of claim 1, wherein a pair of shock absorbers cushion theopening and closing motions of the rotatable main operating lever. 6.The combination according to claim 3, wherein the piston-operated deviceincludes a piston reciprocally movable within an operating cylinder andspring-retracted to its inoperative position.
 7. The combinationaccording to claim 2, wherein a flux-shifter magnetically releases anarmature attached to the trigger arm.